libfstools/overlay.c

   1 /*
   2  * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <sys/stat.h>
  15 #include <sys/types.h>
  16 #include <sys/mount.h>
  17
  18 #include <asm/byteorder.h>
  19
  20 #include <errno.h>
  21 #include <string.h>
  22 #include <stdio.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <glob.h>
  26 #include <errno.h>
  27 #include <dirent.h>
  28 #include <fcntl.h>
  29
  30 #include "libfstools.h"
  31 #include "volume.h"
  32
  33 #ifndef GLOB_ONLYDIR
  34 #define GLOB_ONLYDIR 0x100
  35 #endif
  36
  37 #define SWITCH_JFFS2 "/tmp/.switch_jffs2"
  38 #define OVERLAYDIR "/rom/overlay"
  39
  40 static bool keep_sysupgrade;
  41
  42 static int
  43 handle_rmdir(const char *dir)
  44 {
  45         struct dirent *dt;
  46         struct stat st;
  47         DIR *d;
  48         int fd;
  49
  50         d = opendir(dir);
  51         if (!d)
  52                 return -1;
  53
  54         fd = dirfd(d);
  55
  56         while ((dt = readdir(d)) != NULL) {
  57                 if (fstatat(fd, dt->d_name, &st, AT_SYMLINK_NOFOLLOW) || S_ISDIR(st.st_mode))
  58                         continue;
  59
  60                 if (keep_sysupgrade && !strcmp(dt->d_name, "sysupgrade.tgz"))
  61                         continue;
  62
  63                 unlinkat(fd, dt->d_name, 0);
  64         }
  65
  66         closedir(d);
  67         rmdir(dir);
  68
  69         return 0;
  70 }
  71
  72 void
  73 foreachdir(const char *dir, int (*cb)(const char*))
  74 {
  75         static char *globdir = NULL;
  76         static size_t globdirlen = 0;
  77         struct stat s = { 0 };
  78         size_t dirlen = strlen(dir);
  79         glob_t gl;
  80         int j;
  81
  82         if (dirlen + sizeof("/*") > globdirlen) {
  83                 /* Alloc extra 256 B to avoid too many reallocs */
  84                 size_t len = dirlen + sizeof("/*") + 256;
  85                 char *tmp;
  86
  87                 tmp = realloc(globdir, len);
  88                 if (!tmp)
  89                         return;
  90                 globdir = tmp;
  91                 globdirlen = len;
  92         }
  93
  94         sprintf(globdir, "%s/*", dir);
  95
  96         /* Include GLOB_MARK as callbacks expect a trailing slash */
  97         if (!glob(globdir, GLOB_NOESCAPE | GLOB_MARK | GLOB_ONLYDIR, NULL, &gl))
  98                 for (j = 0; j < gl.gl_pathc; j++) {
  99                         char *dir = gl.gl_pathv[j];
 100                         int len = strlen(gl.gl_pathv[j]);
 101                         int err;
 102
 103                         /* Quick way of skipping files */
 104                         if (dir[len - 1] != '/')
 105                                 continue;
 106
 107                         /* lstat needs path without a trailing slash */
 108                         if (len > 1)
 109                                 dir[len - 1] = '\0';
 110                         err = lstat(gl.gl_pathv[j], &s);
 111                         if (len > 1)
 112                                 dir[len - 1] = '/';
 113
 114                         if (!err && !S_ISLNK(s.st_mode))
 115                                 foreachdir(gl.gl_pathv[j], cb);
 116         }
 117         cb(dir);
 118 }
 119
 120 static void foreach_mount(int (*cb)(const char *, const char *))
 121 {
 122         FILE *fp = fopen("/proc/mounts", "r");
 123         static char line[256];
 124
 125         if (!fp)
 126                 return;
 127
 128         while (fgets(line, sizeof(line), fp)) {
 129                 char device[32], mount_point[32];
 130
 131                 if (sscanf(line, "%31s %31s %*s %*s %*u %*u", device, mount_point) == 2)
 132                         cb(device, mount_point);
 133         }
 134
 135         fclose(fp);
 136 }
 137
 138 void
 139 overlay_delete(const char *dir, bool _keep_sysupgrade)
 140 {
 141         keep_sysupgrade = _keep_sysupgrade;
 142         foreachdir(dir, handle_rmdir);
 143 }
 144
 145 static int
 146 overlay_mount(struct volume *v, char *fs)
 147 {
 148         if (mkdir("/tmp/overlay", 0755)) {
 149                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
 150                 return -1;
 151         }
 152
 153         if (mount(v->blk, "/tmp/overlay", fs, MS_NOATIME, NULL)) {
 154                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n", fs, v->blk);
 155                 return -1;
 156         }
 157
 158         return 0;
 159 }
 160
 161 /**
 162  * ovl_move_mount - move mount point to the new root
 163  */
 164 static int ovl_move_mount(const char *device, const char *mount_point)
 165 {
 166         static const char *prefix = "/tmp/root/";
 167
 168         if (strncmp(mount_point, prefix, strlen(prefix)))
 169                 return 0;
 170
 171         return mount_move(prefix, "/", mount_point + strlen(prefix));
 172 }
 173
 174 static int
 175 switch2jffs(struct volume *v)
 176 {
 177         struct stat s;
 178         int ret, fd;
 179
 180         if (!stat(SWITCH_JFFS2, &s)) {
 181                 ULOG_ERR("jffs2 switch already running\n");
 182                 return -1;
 183         }
 184
 185         fd = creat(SWITCH_JFFS2, 0600);
 186         if (fd == -1) {
 187                 ULOG_ERR("failed - cannot create jffs2 switch mark: %m\n");
 188                 return -1;
 189         }
 190         close(fd);
 191
 192         ret = mount(v->blk, OVERLAYDIR, "jffs2", MS_NOATIME, NULL);
 193         unlink(SWITCH_JFFS2);
 194         if (ret) {
 195                 ULOG_ERR("failed - mount -t jffs2 %s %s: %m\n", v->blk, OVERLAYDIR);
 196                 return -1;
 197         }
 198         selinux_restorecon(OVERLAYDIR);
 199
 200         if (mount("none", "/", NULL, MS_NOATIME | MS_REMOUNT, 0)) {
 201                 ULOG_ERR("failed - mount -o remount,ro none: %m\n");
 202                 return -1;
 203         }
 204
 205         if (system("cp -a /tmp/root/* /rom/overlay")) {
 206                 ULOG_ERR("failed - cp -a /tmp/root/* /rom/overlay: %m\n");
 207                 return -1;
 208         }
 209
 210         if (pivot("/rom", "/mnt")) {
 211                 ULOG_ERR("failed - pivot /rom /mnt: %m\n");
 212                 return -1;
 213         }
 214
 215         if (mount_move("/mnt", "/tmp/root", "")) {
 216                 ULOG_ERR("failed - mount -o move /mnt /tmp/root %m\n");
 217                 return -1;
 218         }
 219
 220         ret = fopivot("/overlay", "/rom");
 221
 222         /*
 223          * Besides copying overlay data from "tmpfs" to "jffs2" we should also
 224          * move mount points that user could create during JFFS2 formatting.
 225          * This has to happen after fopivot call because:
 226          * 1) It's trivial to find mount points to move then (/tmp/root/...).
 227          * 2) We can't do that earlier using /rom/overlay/upper/ as overlay(fs)
 228          *    doesn't support mounts. Mounting to upper dir don't make overlay
 229          *    /propagate/ files to the target dir.
 230          */
 231         foreach_mount(ovl_move_mount);
 232
 233         return ret;
 234 }
 235
 236 int
 237 handle_whiteout(const char *dir)
 238 {
 239         struct stat s;
 240         char link[256];
 241         ssize_t sz;
 242         struct dirent **namelist;
 243         int n;
 244
 245         n = scandir(dir, &namelist, NULL, NULL);
 246
 247         if (n < 1)
 248                 return -1;
 249
 250         while (n--) {
 251                 char file[256];
 252
 253                 snprintf(file, sizeof(file), "%s%s", dir, namelist[n]->d_name);
 254                 if (!lstat(file, &s) && S_ISLNK(s.st_mode)) {
 255                         sz = readlink(file, link, sizeof(link) - 1);
 256                         if (sz > 0) {
 257                                 char *orig;
 258
 259                                 link[sz] = '\0';
 260                                 orig = strstr(&file[1], "/");
 261                                 if (orig && !strcmp(link, "(overlay-whiteout)"))
 262                                         unlink(orig);
 263                         }
 264                 }
 265                 free(namelist[n]);
 266         }
 267         free(namelist);
 268
 269         return 0;
 270 }
 271
 272 static char *overlay_fs_name(int type)
 273 {
 274         switch (type) {
 275                 case FS_EXT4:
 276                         return "ext4";
 277                 case FS_F2FS:
 278                         return "f2fs";
 279                 case FS_UBIFS:
 280                         return "ubifs";
 281                 case FS_JFFS2:
 282                 default:
 283                         return "jffs2";
 284         }
 285 }
 286
 287 int
 288 jffs2_switch(struct volume *v)
 289 {
 290         char *mp, *fs_name;
 291         int type;
 292
 293         if (find_overlay_mount("overlayfs:/tmp/root"))
 294                 return -1;
 295
 296         if (find_filesystem("overlay")) {
 297                 ULOG_ERR("overlayfs not supported by kernel\n");
 298                 return -1;
 299         }
 300
 301         volume_init(v);
 302         mp = find_mount_point(v->blk, 0);
 303         if (mp) {
 304                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
 305                 return -1;
 306         }
 307
 308         type = volume_identify(v);
 309         fs_name = overlay_fs_name(type);
 310
 311         switch (type) {
 312         case FS_NONE:
 313                 ULOG_ERR("no jffs2 marker found\n");
 314                 /* fall through */
 315
 316         case FS_DEADCODE:
 317                 if (switch2jffs(v))
 318                         return -1;
 319
 320                 ULOG_INFO("performing overlay whiteout\n");
 321                 umount2("/tmp/root", MNT_DETACH);
 322                 foreachdir("/overlay/", handle_whiteout);
 323
 324                 /* try hard to be in sync */
 325                 ULOG_INFO("synchronizing overlay\n");
 326                 if (system("cp -a /tmp/root/upper/* / 2>/dev/null"))
 327                         ULOG_ERR("failed to sync jffs2 overlay\n");
 328                 break;
 329
 330         case FS_EXT4:
 331         case FS_F2FS:
 332         case FS_UBIFS:
 333                 if (overlay_mount(v, fs_name))
 334                         return -1;
 335                 if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
 336                         ULOG_ERR("switching to %s failed\n", fs_name);
 337                         return -1;
 338                 }
 339                 break;
 340         }
 341
 342         sync();
 343         fs_state_set("/overlay", FS_STATE_READY);
 344         return 0;
 345 }
 346
 347 static int overlay_mount_fs(struct volume *v, const char *overlay_mp)
 348 {
 349         char *fstype = overlay_fs_name(volume_identify(v));
 350
 351         if (mkdir(overlay_mp, 0755)) {
 352                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
 353                 return -1;
 354         }
 355
 356         if (mount(v->blk, overlay_mp, fstype,
 357 #ifdef OVL_MOUNT_FULL_ACCESS_TIME
 358                 MS_RELATIME,
 359 #else
 360                 MS_NOATIME,
 361 #endif
 362 #ifdef OVL_MOUNT_COMPRESS_ZLIB
 363                 "compr=zlib"
 364 #else
 365                 NULL
 366 #endif
 367                 )) {
 368                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n",
 369                          fstype, v->blk);
 370                 return -1;
 371         }
 372
 373         return 0;
 374 }
 375
 376 enum fs_state fs_state_get(const char *dir)
 377 {
 378         char *path;
 379         char valstr[16];
 380         uint32_t val;
 381         ssize_t len;
 382
 383         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
 384         sprintf(path, "%s/.fs_state", dir);
 385         len = readlink(path, valstr, sizeof(valstr) - 1);
 386         if (len < 0)
 387                 return FS_STATE_UNKNOWN;
 388
 389         valstr[len] = 0;
 390         val = atoi(valstr);
 391
 392         if (val > __FS_STATE_LAST)
 393                 return FS_STATE_UNKNOWN;
 394
 395         return val;
 396 }
 397
 398
 399 int fs_state_set(const char *dir, enum fs_state state)
 400 {
 401         char valstr[16];
 402         char *path;
 403
 404         if (fs_state_get(dir) == state)
 405                 return 0;
 406
 407         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
 408         sprintf(path, "%s/.fs_state", dir);
 409         unlink(path);
 410         snprintf(valstr, sizeof(valstr), "%d", state);
 411
 412         return symlink(valstr, path);
 413 }
 414
 415
 416 int mount_overlay(struct volume *v)
 417 {
 418         const char *overlay_mp = "/tmp/overlay";
 419         char *mp, *fs_name;
 420         int err;
 421
 422         if (!v)
 423                 return -1;
 424
 425         mp = find_mount_point(v->blk, 0);
 426         if (mp) {
 427                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
 428                 return -1;
 429         }
 430
 431         err = overlay_mount_fs(v, overlay_mp);
 432         if (err)
 433                 return err;
 434
 435         /*
 436          * Check for extroot config in overlay (rootfs_data) and if present then
 437          * prefer it over rootfs_data.
 438          */
 439         if (!mount_extroot(overlay_mp)) {
 440                 ULOG_INFO("switched to extroot\n");
 441                 return 0;
 442         }
 443
 444         switch (fs_state_get(overlay_mp)) {
 445         case FS_STATE_UNKNOWN:
 446                 fs_state_set(overlay_mp, FS_STATE_PENDING);
 447                 if (fs_state_get(overlay_mp) != FS_STATE_PENDING) {
 448                         ULOG_ERR("unable to set filesystem state\n");
 449                         break;
 450                 }
 451         case FS_STATE_PENDING:
 452                 ULOG_INFO("overlay filesystem has not been fully initialized yet\n");
 453                 overlay_delete(overlay_mp, true);
 454                 break;
 455         case FS_STATE_READY:
 456                 break;
 457         }
 458
 459         fs_name = overlay_fs_name(volume_identify(v));
 460         ULOG_INFO("switching to %s overlay\n", fs_name);
 461         if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
 462                 ULOG_ERR("switching to %s failed - fallback to ramoverlay\n", fs_name);
 463                 return ramoverlay();
 464         }
 465
 466         return -1;
 467 }